title: Serum ferritin and hemoglobin are independently associated with wider retinal venular caliber: the Tromsø Study 2001-2008.
abstract: OBJECTIVE
  To investigate if markers of iron body stores and hemoglobin are associated with retinal vascular caliber.
  
  
  METHODS
  This was a population-based study including 2993 participants of the fifth and sixth surveys of the Tromsø Study in Norway, conducted in 2001-2002 and 2007-2008. The association between levels of s-ferritin, transferrin saturation, and hemoglobin in the fifth survey and retinal vascular caliber in the sixth survey was assessed by multivariable linear regression models.
  
  
  RESULTS
  Men had higher levels of hemoglobin and s-ferritin than women. Hemoglobin was associated with wider retinal venules in both men and women (mean difference between highest compared to lowest sex-specific quartile: men 5.99 μm, P = 0.001; women 7.28 μm, P < 0.001). S-ferritin was associated with wider retinal venules in men but not women, independent of traditional risk factors (mean difference between highest compared to lowest sex-specific quartile: men 4.21 μm, P = 0.013; women -0.21 μm, P = 0.89). The association in men was attenuated, but still significant, with adjustment for hemoglobin. S-ferritin and level of hemoglobin were not associated with arteriolar caliber in either sex. Transferrin saturation was not associated with retinal vascular caliber.
  
  
  CONCLUSIONS
  Level of hemoglobin was associated with wider retinal venules in both sexes while s-ferritin was associated with wider retinal venular caliber only in men. Men have higher levels of stored iron, and this may underlie the observed sex difference in the association between s-ferritin and retinal vascular caliber.
authors.affiliation: Brain and Circulation Research Group, Department of Clinical Medicine, Faculty of Health Sciences, University of Tromsø, Tromsø, Norway.
authors.forename: Therese
authors.initials: T
authors.lastname: von Hanno
authors.forename: Geir
authors.initials: G
authors.lastname: Bertelsen
authors.forename: Ann Ragnhild
authors.initials: AR
authors.lastname: Broderstad
authors.forename: Tom
authors.initials: T
authors.lastname: Wilsgaard
authors.forename: Ellisiv B
authors.initials: EB
authors.lastname: Mathiesen
mesh_terms: D015415:Biomarkers / Q000097:blood; D002318:Cardiovascular Diseases / Q000097:blood* / Q000453:epidemiology; D005260:Female; D005293:Ferritins / Q000097:blood*; D005500:Follow-Up Studies; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009664:Norway / Q000453:epidemiology; D015995:Prevalence; D011379:Prognosis; D012169:Retinal Vein / Q000473:pathology*; D012189:Retrospective Studies; D012737:Sex Factors; D014699:Venules / Q000473:pathology*
chemical_list: D015415:Biomarkers; D006454:Hemoglobins; D005293:Ferritins
keywords: Tromsø Study; epidemiology; ferritin hemoglobin; microcirculation; retinal vascular caliber